


Donnie's Mistake

by HolyKingWasteLand



Series: Donnie's Anxiety Troubles [1]
Category: Teenage Mutant Ninja Turtles (Bay Movies), Teenage Mutant Ninja Turtles (TV 2012), Teenage Mutant Ninja Turtles - All Media Types
Genre: Angst, Battle, Battle Scars, Blood, Broken Bones, Donatello (TMNT) Needs a Hug, Donatello loves his brothers, Donatello-centric, Emotional Hurt/Comfort, Family Fluff, Fluff, Gen, How Do I Tag, Hurt, Hurt Donatello (TMNT), Hurt/Comfort, Mutant Cure (TMNT), Not Beta Read, Protective, Protective Donatello (TMNT), Serious Injuries, Shapeshifting, Sort Of, We Die Like Men
Language: English
Status: Completed
Published: 2019-08-30
Updated: 2019-08-30
Packaged: 2020-09-30 14:39:53
Rating: Teen And Up Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 3,904
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/20448764
Author URL: https://archiveofourown.org/users/HolyKingWasteLand/pseuds/HolyKingWasteLand
Summary: Donatello gets hit by his own experimental serum, turning him into a giant beast. How will the other turtles fair against their big angry re-mutated brother?





	Donnie's Mistake

**Author's Note:**

> First TMNT fanfic, and I love Donatello so much I literally cried twice last night because I couldn't tell him how important he was or how much I loved him.... so yeah um I love him so i'll do what I do with all of my children
> 
> hurt them.

It was all hypothetical.

That's what Donatello told himself as he added another vile to the mix. Thick leather gloves cover his hands, up to his elbows. He wears protective goggles, and a mask over his mouth to avoid the putrid fumes. He reaches over to pick up another beaker, when he knocks the empty one beside it onto the floor.

The glass shatters, and Donnie sighs, putting his serum filled glass down on the bench. He kneels down and starts collecting the shattered pieces, when he notices a large bottom section of it rolled away underneath his table. He rolls his eyes and crawls closer so he can grab it.

He always taught himself to have a clean work-space, and that that was how you prevented accidents.

Maybe he should have left it for after the serum was put away at a safe distance.

He bumps his head on the underside of the bench and winces; curse his height! He crawls backwards when he feels something drip onto the back of his neck, and roll down his shoulder. He freezes.

That was his first mistake.

Donnie scoots back, abandoning the glass. He peers up onto the bench and sees his mistake played out. 

The serum had fallen when he bumped the table. 

And now he had serum on his skin. Serum that wasn't yet identified. He wasn't sure if it was even going to work yet.

He heaves a sigh of relief. It's not going to work just yet. He's only been fiddling around with the thing for an hour or two, it was nowhere near completed.

See, it was meant to turn mutated humans back into regular humans, but he hadn't found the right balance between the substances yet. Smiling uneasily, he begins checking himself over for any unwanted reactions. Nothing.

He laughs breathily, sitting back down in his chair, completely relaxed.

That was his second mistake.

Suddenly, his fingers grew sharp talons at the ends of them, stabbing through the gloves, his skin turns darker and discoloured. Rough skin turns to sharp scales. His bones crack and shift and _grow,_ and it hurts. He leaves a trail of blood as his skin splits open, and it looks like a murder scene.

He lets out an ungodly scream, tearing his bandanna off as he throws himself to the ground. He leaves scratches on his face, but at least his purple cloth is okay. He only has a moment to be happy for the item, because his spine is shifting next. It bends out of shape, and elongates, and then his legs and arms grow with it. 

Donnie screams, but it sounds more guttural than it did before. He feels his beak changing, shifting, into a long snout. Scales protrude from everywhere and he scratches the ground, whimpering and crying out in pain.

He finally thinks it's over when his bones stop shifting, but suddenly- like he's just been smacked- he has a long drawn out burning sensation.

Then it's over. 

He glances around, scared out of his mind, roaring out of sheer terror as his new giant dark green tail swings around the room. He breaks some equipment, and sends his bench flying into the wall.

That's when the door to his lab finally flies off it's hinges. 

He whips around to see his three brothers standing there, horrified at what they see.

Donatello understands, he's horrified too.

He lets out a vicious cry and tries to push his brother's away _gently._ What he does in reality though, is his giant claw flies out and smacks Michelangelo in the face, the other two only just dodging in time. He baulks and pulls away from them, backing himself into a corner, but the damage is done.

Mikey is down.

Every big brother instinct in him is crying out, trying to get him to _go to him _and _help._ But he can't. Because of this dumb mistake.

"What did you do to our brother?" Leonardo yells, and Donnie isn't sure if he means himself, or Mikey. He croaks out a terrified noise, but it sounds threatening to the other boys, by the looks on both Leo and Raphael's faces.

Raph kneels beside a bleeding Mikey and checks him over for any immediate injuries. Donatello hopes he's okay, he wouldn't be able to forgive himself if Mikey didn't come out alive.

He scratches himself accidentally and roars in pain. Leo takes the sound badly and charges forward.

Leo is going to strike him, and he has no way of telling him what's going on.

Donnie is terrified.

He throws out his claws and hopes Leo jumps away in time, which he does, but not without a hard time.

"Damn- where's Donnie?! What did you do to him!" Raph screams, cradling their youngest brother in his arms.

_I'm right here!_ He tries to scream, but just ends up roaring again.

This is getting them nowhere. He has to think. Fast.

If he keeps fighting back, they're going to get hurt. And he can't handle that thought. So, he doesn't. He stops fighting.

He lays down on the ground, covering his eyes and snout with his big claws. He's shaking, and his tail wraps around him protectively.

Leonardo takes in a sharp breath, "What the..?"

"Hurry up, Leo! We gotta get Mikey outta here!" Raphael growls, hauling Michelangelo up onto his back. Leo takes a hesitant step towards the beast, still holding up his Twin Katanas.

"It's... scared?" Leonardo mumbles, tightening his grip when the beast uncovers it's eyes. He's had a history of deception and being lied to by the enemy just to drop his guard; he won't make the same mistake today.

Donatello chirps softly, trying to tell Leo that he means no harm. It almost appears to work, but then he calls over his shoulder, "Get Mikey to Sensei and come back with some chains. We need answers."

* * *

After they chained him up, the two brothers looked a bit more at ease, so Donnie wasn't complaining. He had tried talking to them, but it was like his ability to talk had been taken away. He sighs, letting out a big breath through his larger-than-usual nostrils. Leo and Raph look on guard again and Donnie has to resist another sigh.

He has no idea when this will wear off- or _if _it even will. 

The other two leave and come back every so often, but Donnie is bored out of his mind. He needs something stimulating, he needs to do _something_. Gosh, he wishes they hadn't chained him up. He truly wishes this hadn't happened, but oh well.

It's a while before they come back, probably an hour or so, and this time they bring April.

Donnie immediately sits up and begins making a fuss. She can't see him like this! He can't hurt her! He roars and ends up snapping his face at them angrily. He can't- and wouldn't- get close to them due to the chains, but he makes it known he doesn't want her there.

When Leo and Raph stand in front of her with their weapons drawn protectively, Donnie nearly cries out of frustration.

Is this what he's going to live like for the rest of his life? Will he ever get to hold his brothers again? Will he ever be able to tell them how much he loves them?

They take April away, and a bit later, Leo brings him food.

Donnie waits for Leo to leave before eating, but the eldest doesn't move. He sits down cross-legged out of reach and waits patiently. Donatello glances at him uneasily before taking a mouthful of noodles. Leo smiles softly, "Who are you? Why are you here?" He gets no verbal response, so he sighs. "I don't know if you're choosing to ignore me, or if you really can't speak."

Donnie almost laughs at that, but it ends up just sounding like rumbles from his chest as his head bobs slightly. Leonardo sighs and stands up. "Well, we'll figure out what to do with you in the morning. Night," He calls almost absentmindedly before exiting the dark room. Donnie bottles up his sadness and continues eating.

He tries not to think about Mikey, but it doesn't really work. He always was the best thinker.

* * *

Donatello wakes up to footsteps. He opens his big eyes and sees Michelangelo limping into the room. He goes to yell at him for being up and about while he's still healing, when he remembers- he can't talk. Roaring would scare him off, and so he sits patiently, watching Mikey wander closer and closer. 

Okay, too close, too close!

Mikey reaches out and puts a gentle hand upon his snout, making Donnie freeze. His fight or flight reflexes are telling him to attack, but his big brother instincts are telling him to be gentle and protect. The latter feeling wins quickly and he relaxes under Mikey's hand.

"Yeah, you're not so scary, huh?" Mikey mumbles, petting him softly with his left hand, his right one is up in a make-shift sling. The same side that Donnie hit. He whimpers and pulls away, but Mikey just steps closer, until he can't move back anymore. "Can you talk, dude?"

Donnie shakes his head side to side slowly, careful to not hit his brother again.

"Oh, I see." Mikey hums in thought, and then just lays down in the ring Donnie has made with his enclosed arms. He makes himself comfortable and then settles back to sleep.

Donnie, however, is now to paranoid to sleep. What if he rolls in his sleep and crushes him? Or his head is too heavy and crushes him? Or he loses control over himself and _crushes him!! _

What if they come in and see Michelangelo? What will they do to him?

He's terrified, and doesn't feel safe any longer. Luckily for him, Mikey only sleeps a few minutes before his arm starts hurting again and he leaves to find Sensei.

Donnie closes himself off; he curls up in a tight ball in the corner of the room, his large scaly back towards the door as a silent "go away". He hears Mikey's footsteps come back, then a sigh, and then his brother leaves again, allowing Donnie to finally breathe again.

He manages to fall asleep, and it seems only minutes before he's being woken again. He turns his head towards the footsteps and sees Leo bringing him another bowl full of something. He looks down and notices cooked fish. He narrows his eyes at it and looks back to Leonardo.

"I uh... I don't know what you like to eat, so here?" He sounds unsure, and the smile is uneasy as he places the fish bowl on the ground. Donnie sniffs it and then begins eating, it's not great, and the fish is a little burnt, but it's fine.

Leo doesn't stick around, just collects the empty bowl and leaves.

He hears talking outside his room, something about them going out and looking for Donatello, and then the house is quiet.

But not for long.

Donnie is fine, until his bones begin shifting again, this time however, they're getting smaller. It's somehow more painful.

He screams, and roars, and cries, and bleeds until he's finally himself again.

The chains are still on him, weighing heavily on his aching limbs, despite the fact that they are much too big for him now. He hiccups and sobs into the cold floor, trying to curl in on himself to stop the dull ache in his bones. His skin is split by his joints, and there are tears here and there from his skin stretching at an alarming rate.

He isn't sure how long he lays there for, in a puddle of his own blood, sweat, and tears. But after a long while, he hears shouting, and then people picking him up gently, and rolling him onto his back.

He lets out a dry sob, and opens his eyes painfully to see his brothers panicking. Sensei says something, and then they're moving. He's gently lifted by someone, and then laid down on a soft bed. Tear tracks line his cheeks and Mikey wipes them away, concern and fear in his eyes.

_I put that there._ His mind supplies bitterly, and Donnie turns his head away from Mikey, not ready to face the guilt. He hears a sigh from the youngest, and then hisses in pain when Leo begins sewing up his major wounds. Sensei gently wipes the wet and dry blood from his skin. Raphael stands off to the side, holding a shaking Mikey in his arms.

He doesn't hear much, just little snippets as he comes in and out of consciousness. Turns out, major blood-loss will make you woozy! Who would've thought?

* * *

He wakes up with a start, throwing himself up as he heaves in struggling breaths. Someone is at his side in an instant and has a hold of him as Donnie coughs and sucks in air. The hold is firm and unwavering, a little too tight for his liking, but he really doesn't want to be touched right now. He struggles a few more seconds before hiss heart begins calming down.

He looks up and sees Raphael's concerned face staring down at him. He tries to smile, but it's more of a grimace. Raph seems to get it, and gently lowers him down onto the bed again.

"How're you feelin'?" He asks gruffly. Donatello just sighs, rolling over onto his side so he doesn't look at Raphael. Because all he can see is the anger, the hate. Raph grunts and then exits the room silently. Donnie wipes his eyes, he's not crying, it's just.. dusty in here.

A few minutes later, Michelangelo enters. He knows because of the _pat pat pat _coming from his steps, sporadic and unusual, just like Mikey. He doesn't turn towards his brother, but when he feels a hand on his shoulder, he panics. He rolls away from Mikey, irritating his injuries, and he looks at his youngest brother with terror in his eyes, holding his hands firm against his chest.

Mikey doesn't try to get close to him again.

Leo tries after Mikey runs out, but Donnie doesn't look at him, just hugs his legs and stares at the floor with wide eyes. "Don?" Leo says softly, kneeling down in front of him. "What's going on, buddy?" He reaches out to Donnie, and the latter freezes, tensing up painfully. Leo quickly pulls away again with a frown. "You can talk to us, you know. We're your family."

Donnie still refuses to say anything, causing Leo to sigh and nod. "Well, we're all here to talk when you're ready, alright?" He stands up and with a regretful look at his younger brother, he leaves. Donnie doesn't watch him go, doesn't see the look, just feels the disappointment.

How is he supposed to face his family like this? Man up Donatello, this isn't the end. They'll forgive you, he tells himself, repeating it like a mantra.

* * *

The next day, Donnie joins them for breakfast. He's smiling softly now, and the others are _ecstatic_.

"Donnie! You're okay! We thought you weren't gonna ever come out-" Raph elbows Mikey in the side and the latter lets out a soft 'oof' as he's cut off. Donnie's smile falters at the action, but he just laughs uneasily.

"Don't mind him, Donnie. I'm glad you're joining us." Leo smiles softly and serves him up some noodles. They've yet to ask him any questions about what happened, and he's hesitant to share. He risks a glance at Mikey and sees the cuts healing over from their fight. He quickly looks away, his smile gone, and the table goes quiet. He's pretty much lost his appetite, so he quickly eats some and then excuses himself back to his room.

He doesn't see the sad looks his brothers give him, but he feels their eyes burning holes in his back. He hates it.

* * *

The next day, he was found by his brothers in the common area. They joined him, Mikey put on the TV, Raph was silently knitting on the lounge, trying to practice as per Splinter's request, and Leo was casually watching alongside Mikey.

Donnie feels crowded. He loves his brothers, really he does, but he can't be around them right now. He just can't do it- everything aches and he just needs an escape from their near constant coddling.

He puts up with it though. He sits, tense, on the lounge. If the others notice, they don't mention it.

And then April walks in.

"Hey guys- Donnie! You're up!" She smiles at the sight of him, and what would usually make him so happy, just makes him feel sick. She runs over to them and hugs him tightly, oblivious to the brothers shaking their heads and trying to tell her not to.

Donatello freezes up, tenses upon contact. He suddenly feels trapped, like he's back in those chains again, lashing out at his family. April feels him tense up and pulls back, but keeps her arms on him. "Hey, you alright?" She asks, and he quickly stands up and pulls away fully.

"Yep! Fine and dandy!" He stretches his words, stumbling backwards to get away- and he trips. Over Mikey. "Ouch..."

Mikey bounces up and kneels next to him. "Oh gosh dude, you okay?"

Donnie freezes when he sees Mikey's face fully in his vision. The cuts are extremely visible, and his own eyes are very wide. He reaches up shakily and touches Mikey's face, hand hovering near the scab, but never touching it. Then, he pulls away as if he's been burned.

He scoots away away away until he's up against the wall, and then he runs out of the room, towards the Dojo, not making eye contact with any of them.

He doesn't hear them talking as he leave, nor Mikey's sad words, he just runs and _runs _and it feels so good to not have to breathe for a moment. But once he's there, the breathing comes back, and so does the shaky hands, and the shaky- well- everything.

He picks up his Bo Staff from where it was sitting idly, and begins hitting the dummy softly. Meagre hits against the dummy's side, then he panics and hits the face instead.

God, get it together Donatello! 

He smacks the dummy, getting harsher and harsher as he gets lost in thought. Pulling his cuts open, his eyes are wide and crazed because he hasn't been sleeping recently, too caught up in the what-if's and could-have-been's.

He doesn't notice someone has entered until they're almost right behind him; to which he spins himself and his Bo Staff around and nearly comes in contact with their head, if not for the person blocking it.

"S-Sensei." Donatello stutters, lowering his staff immediately and takes a step back. Don't corner him, don't corner him, need to run, _have to get away._

"My son, what is going on?" Splinter's calm voice soothes him like aloe vera on a burn. His hands are shaking, and so are his legs, and he's not sure if he can even _talk._ Splinter moves closer, and takes Donatello by his shoulders, trying to ground him. Donnie's heart rate picks up again, but he stays stock still, not even listening to his Sensei's words until: "Understand?"

"Hai, Sensei." He responds automatically, and then rushes out, much to Sensei's displeasure.

* * *

It gets to the point where Donatello bolts the door shut to his room. He can't bear to look at them, see the scars that he left, he just can't. So he stays in his room, hugging himself as he sits in the corner, like when they kids and the others were being mean. Donnie would just resume this position and not come out until said brother apologised.

However, this time, no brother was at fault but him. He got himself into this mess, and then he hurt them.

Tears prick at his eyes and he wipes them away angrily. He can't be near them, he'll hurt them again.

A knock sounds.

Then another.

He doesn't reply.

The knocking ceases for a moment, and then the doorknob is tried. It moves, but the door doesn't budge. The turtle on the other side grunts, and then there's a loud bang against the door.

"Damn," Raph mutters, "this thing's really stuck."

"Either that, or Donnie locked himself in there." Leo says, stress clear in his voice.

The banging gets louder, as they try again and again, and Donnie can't take it. They're hurting themselves for nothing!

"Stop!" He shouts, one hand resting on the door, a power-tool in the other. The banging stops. "I... I'll come out." He undoes the bolts, which takes all of five minutes, and then opens the door. He keeps his eyes on the ground, but it's clear they're a bit red.

"Can I hug you?" Mikey asks, clearly the others have talked to him previously about this, but still, his hands twitch by his sides like he wants to hug him so bad. Donnie sighs, "If you must." And closes his eyes, bracing for impact, but it doesn't come, so he opens them again. Mikey is bouncing on his heels, but stays in place.

"It wasn't your fault I got hurt." Mikey says and Donnie blinks in surprise. "You were scared, that much was obvious. And they said you backed off after I got hurt, so... you couldn't have meant it." So they knew it was him, well, he's glad his brothers can connect the dots alone.

"But you still got hurt! And it was my dumb mistake that made it happen in the first place!" Donnie shouts, looking near tears at any moment. "If I was more careful in the lab, none of this would have happened! I was just trying to help the humans that got mutated but look what I did? I nearly killed you Mikey!"

They all go silent, Leo looks down at the ground, Raph looks away, and Mikey just.. smiles.

"But you didn't." Mikey whispers, but still makes no move to touch him. God, how much did they grill him beforehand? "I'm still standing, and stronger than ever, bruh."

Donnie slowly reaches out and touches Mikey's face, around the scab, and then breaks out into an uneasy smile. "Yeah, yeah you are." He mumbles, bringing his younger brother into a strong (but careful) hug. "I'm so sorry Mikey."

"S'all good." Mikey replies, hugging back just as strongly. "God I missed your hugs." Donnie laughs and Mikey joins in, and soon enough, they're all hugging and laughing.

When they break apart, Leonardo gently touches his shoulder. "I'm glad you're back with us, Donnie. Things haven't been the same around here without you." He says honestly, smiling sadly.

Raphael laughs, "Yeah, and I'm sure your girlfriend will be happy that you're back up and running." 

"Wh-what? She's not my girlfriend!" Donatello blushes and gets his head petted by Raph, who's grinning like a shark. 

"Sure sure, anyways, I'm starving. Let's order a pizza and invite April over!" Mikey suggests, and the others cheer in agreement.

Donatello makes sure to get a good look at his brothers, and remind himself that they're okay. They're not dead, and they don't hate him.

They're okay.


End file.
